Actually, it's tied for #147 in the U.S. Mainland Resorts category. (Tied with J.W.Marriott Camelback Inn in Scottsdale Az and Westin Key West Resort and Marina.) All 20 of the resorts in the Hawaii Resorts category are rated higher. As well as many in other regional categories.
Now, Tortuga Beach Club is a very nice resort. Don't get me wrong. I like it very much. But it is much like several other S.W. Florida resorts. The only other timeshare resorts on the mainland U.S. list were, as I recall, Big Cedar Lodge, and 5 or 6 Disney resorts that had both a hotel and timeshare component. To suggest that Tortuga Beach Club is better than every other HGVC, HGVC affiliate, Marriott, Hyatt, Disney, Westin, and Wyndham timeshare in the mainland U.S. is a stretch.
I'm guessing this is the result of an organized campaign (perhaps by owners) to vote for that particular property to make the list.